The present invention relates to data delivery systems and methods. More particularly, the present invention relates to systems and methods for the optimization of a Media Access Control (MAC) protocol for the enablement of delivering data over long range wireless communication systems, such as communications between an aircraft and surface base stations. In some embodiments, this data delivery system may provide data at high throughput data rates exceeding 100 Mbps to enable the transfer of a wide variety of safety, operational and passenger data.
Communication and information access is imperative to the aviation industry. Earliest commercial aircrafts had primitive voice communication with surface personnel over two way shortwave radio. Not only did this communication dramatically improve flight safety, it also enabled accelerated commercialization of air transport on a level not previously known.
Since then, aircraft have been further upgraded with advent of radar, computers, and even data links to further improve communications. These technologies serve to improve in-flight safety and provide amenities to passengers. However, true broadband high-throughput data uplinks are typically lacking for the airline industry. This is due to a combination of technical and financial constraints which have historically made it impractical, or even impossible, to supply high bit rate data connectivity to an entire fleet of commercial airliners.
However, regardless of hurdles, there is a need to enable broadband wireless communication for aircraft. This need may generally be broken down into operational needs (i.e., maintenance and repair), air safety needs and passenger generated needs.
Operational (maintenance) needs are driven by cost savings the airline may recapture by knowing, real-time, the condition of the aircraft. Gigabytes of flight data are accumulated for each flight but are not easily accessible until after the aircraft has landed (or are even totally inaccessible if not stored for later retrieval). This renders real time engine trends, fuel consumption rates, and parts performance variances unavailable for timely repairs and cost savings. This data is often discarded because downloading the data currently is too slow or too expensive. In newer aircrafts, such as the Boeing 777 or the Airbus 380, some such operational data may be provided on a real time basis to ground personnel in some cases; however, this data is often limited and relies upon low bit rate speeds. Generally, important operational data is collected and downloaded via a wired access port when the aircraft has landed. This data collection, however, is not real time data, and cannot be utilized to preplan maintenance needs.
Safety needs include the ability to identify causes and possibly prevent disastrous accidents. Currently, the flight recorder (i.e., “Black Box”) of an aircraft is accessible after a aircraft crash. A Cockpit Voice Recorder (CVR) is an audio recorder which is often very useful in identifying causes of the accident. Further, depending upon crash location the flight recorder and/or CVR are often never found. Without the flight recorder and/or CVR, it may be impossible to determine what caused the crash. Besides satisfying public curiosity and aiding the bereaved, this causal data is very important in generating protocols and/or safety inspections to prevent future similar accidents. Likewise, if critical aircraft conditions were known by ground personnel in real time, potential disasters could possibly be identified and addressed before they happen. These safety needs are currently unmet given current limited data bandwidth to aircrafts.
Lastly, there are a number of passenger generated needs for larger data bandwidth. For example, unfettered Internet access for passengers could generate high advertising revenues. Likewise, high-speed Internet surfing would facilitate more passenger purchases and commissions for airlines. The limited internet access currently offered by airlines discourages use due to its slow speeds and relative cost.
Those aircraft that are equipped to provide Internet access, or data communication, typically do so at little more than dial-up speeds. This is due, as stated earlier, to current technological and financial hurdles. One simple approach would be to purchase licensed radio frequency (RF) spectrum to devise a dedicated surface to aircraft communication network. However such a system would requires substantial spectrum to service an airline fleet and is thus financially prohibitive. For example, it is expected that 160 MHz of spectrum would be required to achieve the desired performance. A recent purchase by Verizon of 14 MHz cost the company between one and two billion dollars. Of course some spectrum is more valuable than others depending upon services envisioned. Cellular and close to cellular spectrum is considered prime spectrum real estate. Regardless, in order to purchase the necessary spectrum of licensed RF would require an exorbitant capital investment of multiple billions of dollars.
Other approaches to providing data connectivity to aircrafts are to install Satellite Ku Band or Cellular receivers. The weight of a Satellite system is roughly 450 pounds. A cellular system may weigh less, but is still a substantial 125 pounds of excess weight. Weight in an aircraft is directly related to further fuel consumption. Thus, these systems may cost the airline a lot over the course of their usable lifetimes.
In addition to fuel costs, the units themselves are costly. The cellular system has a substantial cost of upwards to one hundred and twenty five thousand dollars upfront per aircraft. The cost for a satellite system may be even larger at upwards to four hundred and fifty thousand dollars. Additionally, the cost of maintenance for the satellite system may tack on an additional hundred thousand dollars or so per year per aircraft, and the array on the aircraft may, in some cases, generate substantial aerodynamic drag.
Additionally, the operational costs of these devices may be very large based upon the size of data being transmitted. It may be costly to send sizable data over satellite or cellular systems.
Lastly, the data rates for these systems are still relatively low; satellite operates at roughly 1.5 Mbps per aircraft, and Cellular systems operate between 0.25 and 2.0 Mbps. Further, signal reliability may be of issue for cellular systems.
Only recently has new technology surfaced which, through sophisticated beamforming protocols, is enabled to affordably provide the required data transfer rates between aircraft and surface base stations at long distances. For an overview of the system utilized to provide this wireless data delivery, see the co-pending application Ser. No. 12/830,324, filed Jul. 4, 2010, entitled “System and Methods for Wireless Broadband Delivery of Data”, by Michael A. Leabman, which is incorporated by reference herein for all purposes, as noted above in the cross reference section.
To maximize spectral efficiency, devices in a wireless networking system, such as the long distance wireless data delivery system disclosed, typically share one or more communication channels. However, two devices simultaneously transmitting on the same communication channel may harmfully interfere with one another. Accordingly, some mechanism is typically employed to arbitrate resource contention, such that devices do not interfere with one another. For example, in the IEEE 802.11 (“WiFi”) protocol, devices use carrier sense to determine whether a communication channel is available for use. Essentially a transmitting device listens to see if any other device is transmitting before itself transmitting. If the channel is clear (i.e., if the transmitting device does not detect any other transmissions), then the device transmits after some random wait time. This technique of using carrier sense to arbitrate resource contention is called Carrier Sense Multiple Access With Collision Avoidance (“CSMA/CA”). The IEEE 802.11-2007 standard is hereby incorporated by reference in its entirety for all purposes.
However, in the case of large distances between transmission source and receiver, delays due to signal propagation may render known protocols inefficient, or even unworkable. Thus, the typical WiFi protocol as discussed above may be inadequate to enable efficient communications when dealing with long range applications, such as the data delivery system between aircraft and base stations as disclosed above.
In view of the foregoing, systems and methods for MAC optimization for long distance wireless communication are disclosed. The present invention provides a novel system and protocols for enabling data communications in long distance situations, such as those between aircraft and base stations.